The present invention relates to a suction system in an engine and more particularly to a suction system for an automotive engine provided with a suction air volume detecting means.
In general, a suction air volume detecting means for an engine is provided in the suction system to detect the air volume sucked into it electrically, and has transistors, condensers, etc. as disclosed in Japanese Patent Publication No. 28174/1977. Such a detecting means is usually located in the vicinity of the engine. Therefore, it is necessary in the detecting means to take into consideration protecting it against the heat radiated from the engine and to prevent it from being affected by electrical wave interference originating from the high voltage ignition system of the engine, etc.
A typical conventional arrangement of a suction air volume detecting means for an automotive engine will be briefly explained below in reference to FIG. 1 of the attached drawings wherein such a means is diagrammatically represented. In the drawing, the reference numeral 1 designates a body of an air cleaner having an air inlet 2, an air cleaner element 3 comprising e.g. filter paper, etc., and an air cleaning chamber 4 formed within body 1. A suction air volume detecting means 5 comprises a flow regulator 6, an air volume detector 7 comprising e.g. a heating wire, and an amplifier 8 comprising various electrical circuit elements including heat sensitive elements such as transistors. An expansion chamber is provided which is adapted to be connected to a suction pipe of an engine (not shown) through a duct 10, expansion chamber 9 having the purpose of reducing the pulsation of the suction air to the engine in order to increase the accuracy of measurement of the air suction volume detecting means 5. However, as explained above, since such a conventional arrangement is provided with no means for protecting it from the heat radiated from the engine and electrical waves from the ignition system, there is the danger of misoperation.